This invention relates in general to certain new and useful improvements in walled enclosures, and more particularly, to the formation of walled enclosures at a site of utilization.
Relatively large storage vessels and similar enclosures, such as grain silos, oil and gas tanks, and other large storage vessels must be constructed or otherwise fabricated at a site of utilization. Due to their large and bulky size, and substantially heavy weight, vessels of this type cannot be readily constructed in a factory and transported to a site of use.
There have been many proposals and indeed, some undertakings to construct components of a large storage vessel, such as side wall segments, in a factory and thereafter assemble these components at the site of utilization. However, most of these storage vessels must be liquid-tight and in many cases gas-tight, and if the various components are not properly mated with a highly critical tolerance, then these objects cannot be fulfilled. Consequently, fabrication of mating components in a factory with an on-site assembly of the components to form a large storage vessel, has not proved to be very satisfactory, and has also been found to be quite costly.
As a result of the deficiencies in constructing a storage vessel from mating component parts, most storage vessels have been erected in a field or other site of utilization. Most of these storage tanks or other storage vessels are made of steel or other heavy structural metals and this, of course, requires a transport of the sheet metal and other materials which are used in the fabrication of the tank to the construction site. Furthermore, erecting equipment, welding equipment, and other forms of metal fabrication and metal working equipment must also be transported to the construction site. Thus, a very substantial portion of the cost of erecting a large metal storage vessel resides in the labor of material handling and the assembly and disassembly of the erecting equipment and supporting structures.
Notwithstanding the substantially high cost in erecting a metal storage structure, these structures inherently suffer from several disadvantages which seriously limit their use. If the storage vessel is designed to contain a corrosive liquid or other corrosive contents, the vessel must be properly lined with glass or other corrosive resistant materials which again substantially increases the cost of the vessel. Furthermore, due to the very significant weight of the steel and other structural metals which are used in the fabrication of metal storage vessels, a fairly substantial foundation or base must be applied to the ground or other supporting surface for erecting the storage vessel. In addition, these metal storage vessels are usually subject to a fair amount of maintenance which increases the operating costs thereof.
In order to overcome the problems inherent with the fabrication and use of metal storage vessels, there have been several attempts to fabricate storage vessels from fiber reinforced materials, such as fiberglass, or from other forms of plastic materials. One such proposal is described in U.S. Pat. No. 3,337,384, which relies upon a system for fabricating wall structures formed of an expandable polystyrene material. In this case, expandable polystyrene is applied in the form of a continuous spiral strip to form a vessel wall. This form of system suffers many disadvantages including a relatively low strength. Consequently, the overall size of the vessel which can be produced in accordance with this system is very limited.
Another proposal for forming a non-metallic tank at an on-site location is taught in U.S. Pat. No. 2,729,268, which relies upon the winding of a storage vessel with resin impregnated fiber material, in a manner very similar to the formation of continuous tubes such as pipe and the like. Again, by the very nature of the device taught, the overall size of the vessel is limited and furthermore, a very substantial amount of fiber containing strand material must be employed which very substantially increases the overall cost of the vessel.
A further method of forming a fiber containing reinforced plastic tank is disclosed in U.S. Pat. No. 2,808,097, which also employs a rotating mandrel to generate a series of vertically superimposed cylindrical rings. This system is extremely complex and requires a substantial amount of manual labor, and thereby materially increases the cost of erecting the vessel.
It is therefore the primary object of the present invention to provide a method and apparatus for fabricating storage vessels from fiber containing reinforcing materials which substantially reduces material handling and labor requirements in assembling the storage vessel.
It is another object of the present invention to provide an improved apparatus and method of the type stated which lends to a very economical construction of on-site storage vessels.
It is a further object of the present invention to provide a method and apparatus of the type stated which permits the fabrication and construction of relatively large storage vessels at a site of utilization and which are capable of containing substantial amounts of and a wide variety of stored materials.
It is an additional object of the present invention to provide a storage vessel which is fabricated from reinforced plastic materials, and which is relatively light in weight, when compared to similar metal structures, but which is, nevertheless very durable and sturdy, requiring little, if any, subsequent maintenance.
It is yet another salient object of the present invention to provide a storage vessel of the type stated which can be fabricated with the same apparatus from a wide variety of reinforced plastic material compositions in order to provide the desired material storage characteristics.
With the above and other objects in view, our invention resides in the novel features of form, construction, arrangement and combination of parts presently described and pointed out in the claims.